Re: Explicitly avoid GC of objects?
On Tuesday, 21 May 2019 at 11:54:08 UTC, Robert M. Münch wrote:
Is there a trick to accomplish 2 when objects are created from
different scopes which need to be kept? So, I have one function
creating the objects and one using them. How can I keep things
on the stack between these two functions?
How is 3 done? Is this only useful for static variables?
I'll try to describe rules 2 and 3 as simply as possible: As long
as you can access the pointer to gc allocated memory in D it will
not be freed.
So whether that pointer lives on the stack:
int* foo() {
return new int;
}
void bar() {
int* a = foo();
c_fn(a);
}
In static or thread local memory:
int* a;
__gshared int* b;
void bar() {
a = new int;
c_fn(a);
b = a;
c_fn(b);
}
Or on the heap:
class D {
int* a;
}
void bar() {
D d = new D(new int);
c_fn(d.a);
}
Doesn't really matter.
Re: "if" statement
On Sunday, 24 March 2019 at 12:45:13 UTC, Francesco Mecca wrote:
https://run.dlang.io/is/zRcj59
```
alias Alg = Algebraic!(int, string);
void main()
{
int n = 2;
Alg value;
value = n == 2 ? 2 : "string";
}
```
The original code used SumType but the effect is the same.
I suppose that I could write the following:
```
if(n == 2) value = 2;
else value = "string";
```
Is there a workaround for this that maintains a similar
syntactic structure?
is this behaviour accepted or should the compiler translate the
first case in the second?
You can achieve the same thing by just constructing your
algebraic type earlier:
value = n == 2 ? Alg(2) : Alg("string");
Re: How to pass variables to string mixins?
On Tuesday, 26 February 2019 at 00:07:54 UTC, Victor Porton wrote:
I want to create a string mixin based on a supplementary
variable (name2 below):
Let we have something like:
mixin template X(string name) {
immutable string name2 = '_' ~ name;
mixin("struct " ~ name2 ~ "{ int i; }");
}
But it would create variable name2 inside X, which should not
be created. How to solve this problem?
Your best bet is to just not declare anything in a mixin template
that you don't want included:
mixin template X(string name) {
mixin("struct _" ~ name ~ "{ int i; }");
}
Or don't use mixin templates:
template X(string name) {
immutable string name2 = '_' ~ name;
enum X = "struct " ~ name2 ~ "{ int i; }";
}
mixin(X!("foo"));
Re: Disable dub from checking internet before building
On Sunday, 24 February 2019 at 22:51:45 UTC, 0x wrote: How to disable dub from checking internet before building, it's slowing down build whenever it does this. Its not too well described but --nodeps skips dependency resolution (just uses the locked dependencies). Since dub only does requests for dependency resolution this stops any requests.
Re: How to create a class-valued variable?
On Tuesday, 19 February 2019 at 22:04:58 UTC, Victor Porton wrote:
What is the right way to store in a structure a class (not an
instance) derived from a given interface(s)?
What are you trying to do with the "class"? If you just want a
static "reference" to it you can use an `alias`:
class A {}
struct B {
alias C = A;
}
new B.C();
If you want dynamic information on the type you can use TypeInfo:
class A {}
struct B {
TypeInfo i;
}
B b;
b.i = typeid(A);
b.i.factory();
Or more simply if you just want to construct instances, just use
a delegate:
interface I {}
class A : I {}
struct B {
I delegate() factory;
}
B b;
b.factory = () => new A();
b.factory();
You *can't* do something like the following because types need to
be validated at compile time:
struct A {
Class cls;
}
A a;
a.cls b;
b.run();
Re: Should D file end with newline?
On Sunday, 10 February 2019 at 02:12:43 UTC, Jonathan M Davis wrote: On Saturday, February 9, 2019 2:19:27 PM MST Victor Porton via Digitalmars- d-learn wrote: ISO C++ specifies that the C++ file must end with a newline. Should D file end with newline, too? No, there is no need to end D files with a newline. I would guess that the vast majority of D files end with a closing brace. I just looked at a bunch of files in the standard library for the heck of it, and almost all of the ones I looked at ended with a closing brace. And those that didn't ended with something like an enum declaration and not a newline. Personally, I don't leave newlines at the end of files, because it looks messy. I don't even recall doing that in C++, though I do recall that there supposedly be a rule about it. It seems like a pretty bizarre requirement to me, but regardless, I'm quite sure that D does not have that requirement. - Jonathan M Davis Doing a quick a quick tail on all the source files for dmd, druntime and phobos, I only found 6 source files that ended in a curly brace and 2 ending in a 'g'. All others ended with a newline. Its certainly not required but it is common in the style guides I've seen and I personally have my editor automatically insert a newline.
